The following patents and/or patent applications are herein incorporated by reference:
U.S. Pat. No. 5,262,098, titled xe2x80x9cMethod And Apparatus For Fabricating Bichromal Balls For A Twisting Ball Displayxe2x80x9d, by Crowley et al. issued on Nov. 16, 1993,
U.S. Pat. No. 4,126,854, titled xe2x80x9cTwisting Ball Panel Displayxe2x80x9d, by Sheridon issued on Nov. 21, 1978,
U.S. Pat. No. 5,825,529, titled xe2x80x9cGyricon Display With No Elastomer Substratexe2x80x9d, by Crowley issued on Oct. 20, 1998,
U.S. Pat. No. 5,262,098, titled xe2x80x9cMethod And Apparatus For Fabricating Bichromal Balls For A Twisting Ball Displayxe2x80x9d by Crowley et al. issued Nov. 16, 1993,
U.S. patent application Ser. No. 09/037,767, titled xe2x80x9cCharge Retention Islands For Electric Paper And Applications Thereofxe2x80x9d by Howard et al. filed on Mar. 10, 1998, and assigned to the same assignee.
U.S. patent application Ser. No. 08/716,672, titled xe2x80x9cTwisting-Cylinder Displayxe2x80x9d by Sheridon et al. filed on Sep. 13, 1996, and assigned to the same assignee.
This invention relates generally to forming bichromal elements to be used in a gyricon display, and more specifically provides a new method and apparatus for supplying hardenable liquid to the surfaces of a spinning disk configuration used to fabricate the bichromal elements.
Gyricon sheet material, also known as electric paper, is known in the art. U.S. Pat. No. 4,126,854, titled xe2x80x9cTwisting Ball Panel Displayxe2x80x9d, by Sheridon, issued on Nov. 21, 1978, and incorporated by reference hereinabove describes how to make and use gyricon sheet material containing bichromal spherical elements. In essence, U.S. Pat. No. 4,126,854 describes a thin transparent sheet having many of the attributes of paper. That is, the sheet is lightweight, flexible, can be easily read in ambient light, and retains displayed information for long periods of time with needing to refresh the displayed information.
The sheet comprises an elastomeric host material which is heavily loaded with substantially hemispherically colored bichromal spherical elements. Each hemisphere is differently colored, such as black and white, red and white or any other combination of colors desired. Each element is further contained within its own substantially spherical cavity in a dielectric liquid. When an electric field is placed across the sheet material the elements rotate such that they line up with the electric field. The elements can therefore be rotated to display either colored hemisphere or even to display a portion of both hemispheres.
U.S. Pat. No. 5,825,529, titled xe2x80x9cGyricon Display With No Elastomer Substratexe2x80x9d, by Crowley, issued on Oct. 20, 1998, and incorporated by reference hereinabove describes another embodiment of gyricon material. As described in U.S. Pat. No. 5,825,529, the spherical elements are closely packed in a stable arrangement, such as a hexagonally packed monolayer directly in the dielectric liquid. The elements in the dielectric fluid are then sandwiched between two retaining members and sealed in. In operation, this embodiment works as described above.
U.S. patent application Ser. No. 09/037,767, titled xe2x80x9cCharge Retention Islands For Electric Paper And Applications Thereofxe2x80x9d by Howard et al. filed on Mar. 10, 1998 and incorporated be reference hereinabove describes yet another embodiment of gyricon sheet material. In U.S. patent application Ser. No. 09/037,767 a sheet material is described similar in nature to the sheet material described in U.S. Pat. No. 4,126,854. However, in U.S. patent application Ser. No. 09/037,767 several different populations of bichromal elements are used to implement grey scale, highlight color and additive full color. The different populations of the bichromal elements are disposed in addressable subpixel areas.
U.S. patent application Ser. No. 08/716,672, titled xe2x80x9cTwisting-Cylinder Displayxe2x80x9d by Sheridon et al. describes yet another embodiment of a display utilizing rotating bichromal elements. In U.S. patent application Ser. No. 08/716,672 a display is described which uses substantially cylindrical elements. As in the earlier described embodiments, the cylinders reside in a dielectric liquid and their orientation can be changed by applying an electric field.
What each of these embodiments have in common is that all use a rotating bichromal element. Many methods are known in the art for forming bichromal elements, for instance, monochromatic elements may first be formed and then coated from one direction in a vacuum evaporation chamber. U.S. Pat. No. 5,262,098, titled xe2x80x9cMethod And Apparatus For Fabricating Bichromal Balls For A Twisting Ball Displayxe2x80x9d by Crowley et al. issued Nov. 16, 1993, and incorporated by reference hereinabove describes a method using a spinning disk technique. In essence, a hardenable liquid is fed to each of the surfaces of a spinning disk. The hardenable liquids meet at the edge of the disk and form a bichromal ligament that is propelled away from the disk. The distal end of the bichromal ligament breaks up into droplets forming bichromal spheres. In a variation on this method described in U.S. patent application Ser. No. 08/716,672, high-viscosity hardenable liquids are used to create bichromal cylinders.
In both cases, two different hardenable liquids must be supplied to the spinning disk, one to each of the opposed surfaces. U.S. Pat. No. 5,262,098 describes a feed mechanism which uses a rotatable dispensing assembly with two liquid metering members with the rotatable disk supported therebetween. The lower metering member includes a spindle portion, mountable upon and rotatable by a motor, a coupling extension having a central bore for receiving liquid, a number of radially extending, upwardly angled liquid supply ports, a circular reservoir, and a circular metering lip for delivering a thin layer of liquid to the lower surface of the spinning disk. The upper metering member encircles the coupling extension and is secured in place by a locking nut. The upper metering member an inner groove communicating with a number of radially extending, downwardly angled liquid supply ports which in turn, communicate with a circular reservoir and a circular metering lip for delivering a thin layer of liquid to the upper surface of the disk. A stationary liquid delivery assembly is seated upon the rotatable dispensing assembly for delivering the two liquids to their respective surfaces of the disk.
While the feed mechanism is quite satisfactory for delivering the two liquids to the their respective surfaces of the disk, during periods of extended use, the system tends to clog preventing proper dispensing of the liquids to their respective surfaces. The present invention provides an improved apparatus and method of use which exhibits reduced clogging when used for extended periods of time.
Further advantages of the invention will become apparent as the following description proceeds.
Briefly stated and in accordance with the present invention, there is provided an apparatus for fabricating bichromal elements comprising a separator member having a central rotating point, the separator member having first and second spaced apart, opposed surfaces with an edge region in contact with both of said opposed surfaces. The spacing between the opposed surfaces varies with the distance outwardly from the central rotating point such that the spacing is the largest at the central rotating point and the spacing decreases outwards from the central rotating point and the spacing is a minimum at the edge region. Further, each of the opposed surfaces has a substantially annular cup spaced apart from and substantially surrounding the central rotating point. The apparatus for fabricating bichromal elements also includes apparatus for dispensing first and second differently colored hardenable liquids in the cups of the first and second surfaces, respectively, and an apparatus for substantially uniformly spreading the liquid material in the annular cups located in the first and second surfaces and for substantially uniformly spreading the liquid material from the cups over the first and second surfaces toward said edge region to form a reservoir of liquid material outboard of said edge region, and for forming ligaments from said reservoir.